Monday, February 06, 2017

LASIK is a two step laser vision correction procedure to improve vision. The first step is creating a flap in the cornea in the front of the eye.

Watch this episode of A State of Sight with Isaac Porter, MD to learn more about the first part of LASIK eye surgery.

Welcome to A State of Sight, I’m Isaac Porter and this is your update in ophthalmology and eyecare from Raleigh. Today, I would like to explain the first step of LASIK, which is a

two step procedure.

The first step of LASIK is creating a flap in the cornea and the second step is changing the shape of the cornea to include the power needed in glasses or contact lenses onto the eye. When LASIK was first performed in the 1990s, this flap was created in the front of the cornea with a machine called a microkeratome. Later, with great advances in modern technology, the femtosecond laser was used to create this flap.

For this step, we use the Zeiss VisuMax laser and we really like this advanced femtosecond laser. It's very comfortable for the patient with only a gentle touch on their eye. Also, it is a very precise laser that creates accurate flaps. This accuracy also enables it to be the only laser approved for SMILE laser eye surgery, the latest vision correction procedure.

From the patient’s perspective, first they lie on the bed of the laser. We operate on one eye at a time so we cover the other eye. We usually treat the right eye first. We put a safety device in the patient’s eyelids so they don’t have to worry about blinking.

Next, they look at a ring of lights on the laser while this laser comes very close to the eye. When the laser is close, the patient can see a green target light and they will feel a very gentle pressure as the laser comes right onto the surface of the cornea. Because the pressure is so light, patients are able to see throughout the procedure.

The laser treatment lasts less than 20 seconds per eye. Many, many laser pulses are placed in the cornea to create a flap. Then the eye is released and we will switch over to repeat the same procedure for the left eye.

When I first heard about a laser creating a flap, I wondered how a laser could treat the cornea and create a flap without affecting the layers above it or going deeper into the layers below. Technically, the way this laser works is by focusing the laser energy at a very precise depth and location in the cornea.

Femtosecond lasers are very, very fast and the individual pulses from the laser are measured in femtoseconds. A femtosecond is a very short fraction of a second. To give you an idea how short a femtosecond is, a femtosecond relates to one second in about the same way that one second relates to 32 million years. So if you think about the number of seconds in 32 million years, you can estimate how many femtoseconds are in one second.

Since the femtosecond laser is so fast, it is able to make lots of pulses in the cornea during the treatment time. Each pulse from the laser creates a tiny air bubble in the cornea. Once all of these pulses and bubbles are connected together in a layer, a flap is created which then can be lifted for the second step of LASIK - changing the shape of the cornea.

We will tell you more about that following step in our next episode of A State of Sight. If you have any questions about this first step, please post and we will be happy to answer them. We hope to see you again soon next time on A State of Sight.